Field of the Invention
The present invention relates to image sensors and image capture apparatuses using image sensors.
Description of the Related Art
Recently, the size of electronic devices having an imaging function, such as digital cameras and mobile phones, has been reduced, and simultaneously, the number of pixels in an image sensor has been increased, which leads to a tendency to an increase in the circuit density within an image sensor.
However, if the circuit density increases, a problem arises in that failures are more likely to occur. For example, assuming a failure in a plurality of holding circuits embedded in an image sensor, Japanese Patent Laid-Open No. 2012-60334 discloses a configuration in which a redundant holding circuit and a 1-bit storage cell are provided.
According to Japanese Patent Laid-Open No. 2012-60334, even if a failure occurs, a function of the image sensor can be maintained by using the redundant holding circuit and the 1-bit storage cell in place of a holding circuit and a 1-bit storage cell that have failed. Provision of more redundant members enables more failures to be dealt with, but the circuit scale increases, and a necessary mounting area also increases. If the density is further increased in order not to increase the mounting area, failures will be more likely to occur. Accordingly, it is necessary to appropriately provide a redundant circuit with which an increase in the circuit scale due to unnecessary redundancy is prevented while sufficient fault-tolerance is maintained, but this point is not considered in Japanese Patent Laid-Open No. 2012-60334.